SITE INFORMATION AND CORRESPONDENCE

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r Mr. Victor Izzo August 28, 1994 Page 2 M-8, which is adjacent to the sewer line, showed the highest TCE concentration in the first ground water unit. All monitoring wells adjacent to the sewer show detectable levels of TCE. Also since the TCE discharge to the sewer line occurred over 20 years ago, it is likely that samples directly from the sewer would not detect TCE. Response: The samples referred to in the statement taken from the RI are those collected in 1992 specifically to detect whether the sewer is a source, related to work done for the Regal Almond case. These samples were not included in the RI report, and have been provided with this letter for your review. They were reported verbally to RWQCB at our meeting of July 22, 1993. The basis of the sampling was that coffee waste discharged to the sewer produces a false positive for phenol using EPA Method 625, although it does not actually contain phenol. A sample collected from the sewer manhole on Industrial Avenue showed 60 parts per billion (ppb) phenol, while samples taken from wells located close to the sewer line (M-313, M-813) collected on the same day, showed no detectable phenol signature. This indicates that the sewer is not currently leaking, and supports the hypothesis that the southward trend of the TCE plume is primarily due to the former southward hydraulic gradient (see response to Comment IV). Comment 111: Section 4.2.3 Soil Vapor Extraction, Paragraph 4; This paragraph provides only a cursory description of the eight months of vapor extraction system results following 10 January 1988 start-up at vapor extraction well VE-4. During those months the concentration leaving the extraction well increased from nondetect to over 10 ppm of TCE. This increase indicates a. source area within the sphere ofinfluenceLof VE-4, but not right at the location of VE-4. This source are& should be identified, and its lateral and vertical extent determined, in order to more effectively remediate it. Response: The vapor extraction pilot test has been reported in many numerous documents to the RWQCB, including the Remedial Measures Report, 1989, and the Vacuum Extraction Systems Status Report, dated January 1994, among others. The presence of an operating manufacturing facility precluded any previous investigations beneath the decaffeination building area. Now that the facility is not operating, there is the potential that the buildings may be removed. If that occurs, further drilling in the area will be possible. Until that time, as we have reported to you in the most recent submittal, the Water Quality Site Assessment, soil vapor extraction will continue using the existing systems to ensure vadose zone remediation.